| 1. |
- Goluchowska, Karolina, et al.
(författare)
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The role of crustal contamination in magma evolution of Neoproterozoic metaigneous rocks from Southwest Svalbard
- 2022
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Ingår i: Precambrian Research. - : Elsevier. - 0301-9268 .- 1872-7433. ; 370
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Tidskriftsartikel (refereegranskat)abstract
- Late Neoproterozoic metavolcanic rocks occur along the Southwest coast of Svalbard. The protoliths of the metavolcanic rocks from Wedel Jarlsberg Land and Nordenskiold Land are mainly diabase, basalt and felsic tuff of tholeiitic affinity associated with continental magmatism. We investigate the magma evolution of the meta-volcanic rocks paying particular attention to processes of magma-crust interaction and assess potential sources of crustal contamination. These goals are achieved by employing trace element geochemistry, as well as Sr and Nd isotope geochemistry. Metavolcanic rocks from the South (Orvindalen and Werenskioldbreen) have higher LREE, LILE and Th compared to rocks from the North (Nordenskiold Land), which are relatively enriched in Sr. Incompatible element ratios like Th/La, Th/Nb, La/Nb, Th/Yb and Nb/Yb also decrease from South to North. The Nd-143/Nd-144(635 Ma) ranges from 0.511396 to 0.512356 and increases from South to North. For Sr isotopes, the metavolcanic rocks show a wide range, however in the South we observe Sr-87/Sr-86(635 Ma) of 0.70407-0.73043 and in the North Sr-87/Sr-86(635 Ma) of 0.70410-0.71028. Energy Constrained - Assimilation and Fractional Crystallization (EC-AFC) modelling indicates that the extent of magma contamination is highest in the South. Additionally the modelling suggests fractional crystallization and assimilation of granulite or amphibolite followed by shale for the metavolcanic rocks in the South and for the North mixtures of carbonate and shale contributed. This geographical pattern of assimilation reflects the upper crustal metasedimentary sequences, where phyllites are common in the South (Orvindalen and Werenskioldbreen) and carbonates are more common in the North (Nordenskiold Land). Density contrasts and impermeable layers within the continental crust would likely have acted as barriers to ascending magma, forcing it to stall and providing opportunities for magma-crust interaction.
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| 2. |
- Barnes, Christopher, et al.
(författare)
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High-spatial resolution dating of monazite and zircon reveals the timing of subduction–exhumation of the Vaimok Lens in the SeveNappe Complex (Scandinavian Caledonides)
- 2019
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Ingår i: Contributions to Mineralogy and Petrology. - : Springer Berlin/Heidelberg. - 0010-7999 .- 1432-0967. ; 174:1
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Tidskriftsartikel (refereegranskat)abstract
- In-situ monazite Th–U–total Pb dating and zircon LA–ICP–MS depth-profiling was applied to metasedimentary rocks from the Vaimok Lens in the Seve Nappe Complex (SNC), Scandinavian Caledonides. Results of monazite Th–U–total Pb dating, coupled with major and trace element mapping of monazite, revealed 603 ± 16 Ma Neoproterozoic cores surrounded byrims that formed at 498 ± 10 Ma. Monazite rim formation was facilitated via dissolution–reprecipitation of Neoproterozoic monazite. The monazite rims record garnet growth as they are depleted in Y2O3 with respect to the Neoproterozoic cores. Rims are also characterized by relatively high SrO with respect to the cores. Results of the zircon depth-profiling revealed igneous zircon cores with crystallization ages typical for SNC metasediments. Multiple zircon grains also exhibit rims formedby dissolution–reprecipitation that are defined by enrichment of light rare earth elements, U, Th, P, ± Y, and ± Sr. Rims also have subdued Eu anomalies (Eu/Eu* ≈ 0.6–1.2) with respect to the cores. The age of zircon rim formation was calculated from three metasedimentary rocks: 480 ± 22 Ma; 475 ± 26 Ma; and 479 ± 38 Ma. These results show that both monazite and zircon experienced dissolution–reprecipitation under high-pressure conditions. Caledonian monazite formed coeval with garnet growth during subduction of the Vaimok Lens, whereas zircon rim formation coincided with monazite breakdown to apatite, allanite and clinozoisite during initial exhumation.
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| 3. |
- Bazarnik, Jakub, et al.
(författare)
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Reinterpretation of a major terrane boundary in the northern Svalbard Caledonides based on metamorphic fingerprinting of rocks in northern Spitsbergen
- 2023
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Ingår i: Canadian journal of earth sciences (Print). - : Canadian Science Publishing. - 0008-4077 .- 1480-3313. ; 60:8, s. 1188-1205
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Tidskriftsartikel (refereegranskat)abstract
- Tectonic models for development of the Svalbard Caledonides depend on reliable assessment of the metamorphic evolution of the various basement provinces involved. The Mosselhalvoya Group (MG) and the Atomfjella Complex (AC) have previously been assigned to the Nordaustlandet andWest Ny-Friesland terranes, respectively. New analytical data and petrographic observations indicate that both units experienced two-stage metamorphism under similar pressure-temperature (P-T) conditions. Two stages of amphibolite facies metamorphism (M1 and M2) are clearly recorded by garnet and staurolite porphyroblast textures. The results of thermodynamic phase equilibrium modeling indicate that peak M2 metamorphism occurred at similar to 7-7.5 kbar and 590-600 degrees C in both units. Zirconium-in-rutile trace element thermometry confirms the temperature estimates for M1 and M2 stages of metamorphism. Monazite chemical Th-U-Pb dates from the MG resolve a two-stage garnet growth at 444 +/- 7 Ma (M1) and 423 +/- 6 Ma (M2). In contrast, monazite dated in the AC defines a single age of 420 +/- 4 Ma interpreted as M2 growth. We suggest M2 was coeval with early strike-slip motion along the Billefjorden Fault Zone, whereas M1 reflects initial tectonic burial of the studied units. The similarity in metamorphic history between the both units suggests that the boundary between them is a subordinate thrust fault within the Atomfjella thrust stack rather than a major boundary separating the Nordaustlandet and West Ny-Friesland terranes. The MG should be included within the West Ny-Friesland terrane and the tectonic boundary with the Nordaustlandet terrane is likely the Eolussletta Shear Zone.
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| 4. |
- Bazarnik, Jakub, et al.
(författare)
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U-Pb zircon dating of metaigneous rocks from the Nordbreen Nappe of Svalbard's Ny-Friesland suggests their affinity to Northeast Greenland
- 2019
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Ingår i: Terra Nova. - : WILEY. - 0954-4879 .- 1365-3121. ; 31:6, s. 518-526
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Tidskriftsartikel (refereegranskat)abstract
- SIMS U-Pb zircon dating of metaigneous rocks of the Nordbreen Nappe from the West Ny-Friesland terrane (Eastern Basement Province of Svalbard) yields crystallization ages of 1,761 +/- 4 Ma for a felsic metatuff and 1,373 +/- 4 Ma for a metagabbro dyke. The Palaeoproterozoic age of the metatuff is similar to previously obtained ages for various felsic rocks from the study area, whereas the Mesoproterozoic age of the metagabbro has not been thus far documented on Svalbard. However, a similar age pattern has been reported from Northeast Greenland. Therefore, we conclude that the West Ny-Friesland terrane can be correlated with age equivalent units of Northeast Greenland. We also explore similarities and dissimilarities between the study area and other terranes of Svalbard and speculate on regional-scale correlations. Together, the presented new ages provide critical piercing points in palaeogeographic reconstructions of the relatively poorly understood circum-Arctic region.
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| 5. |
- Bukala, Michal, et al.
(författare)
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Brittle deformation during eclogitization of early Paleozoic blueschist
- 2020
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Ingår i: Frontiers in Earth Science. - LAUSANNE SWITZERLAND : Frontiers Media SA. - 2296-6463. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- The Tsakkok Lens of the Scandinavian Caledonides represents the outermost Baltican margin that was subducted in late Cambrian/Early Ordovician time during closure of the Iapetus Ocean. The lens predominantly consists of metasedimentary rocks hosting eclogite bodies that preserve brittle deformation on the mu m-to-m scale. Here, we present a multidisciplinary approach that reveals fracturing related to dehydration and eclogitization of blueschists. Evidence for dehydration is provided by relic glaucophane and polyphase inclusions in garnet consisting of clinozoisite + quartz +/- kyanite +/- paragonite that are interpreted as lawsonite pseudomorphs. X-Ray chemical mapping of garnet shows a network of microchannels that propagate outward from polyphase inclusions. These microchannels are healed by garnet with elevated Mg relative to the surrounding garnet. Electron backscatter diffraction mapping revealed that Mg-rich microchannels are also delimited by low angle (<3 degrees) boundaries. X-ray computed microtomography demonstrates that some garnet is transected by up to 300 mu m wide microfractures that are sealed by omphacite +/- quartz +/- phengite. Locally, mesofractures sealed either by garnet- or omphacite-dominated veins transect through the eclogites. The interstices within the garnet veins are filled with omphacite + quartz + rutile + glaucophane +/- phengite. In contrast, omphacite veins are predominantly composed of omphacite with minor apatite + quartz. Omphacite grains are elongated along [001] crystal axis and are preferably oriented orthogonal to the vein walls, indicating crystallization during fracture dilation. Conventional geothermobarometry using omphacite, phengite and garnet adjacent to fractures, provides pressure-temperature conditions of 2.47 +/- 0.32 GPa and 620 +/- 60 degrees C for eclogites. The same method applied to a mesoscale garnet vein yields 2.42 +/- 0.32 GPa at 635 +/- 60 degrees C. Zirconium-in-rutile thermometry applied to the same garnet vein provides a temperature of similar to 620 degrees C. Altogether, the microchannels, microfractures and mesofractures represent migration pathways for fluids that were produced during glaucophane and lawsonite breakdown. The microfractures are likely precursors of the mesoscale fractures. These dehydration reactions indicate that high pore-fluid pressure was a crucial factor for fracturing. Brittle failure of the eclogites thus represents a mechanism for fluid-escape in high-pressure conditions. These features may be directly associated with seismic events in a cold subduction regime.
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| 6. |
- Bukała, Michał, et al.
(författare)
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UHP metamorphism recorded by phengite eclogite from the Caledonides of northern Sweden : P-T path and tectonic implications
- 2018
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Ingår i: Journal of Metamorphic Geology. - : Wiley. - 0263-4929 .- 1525-1314. ; 36:5, s. 547-566
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Tidskriftsartikel (refereegranskat)abstract
- The Seve Nappe Complex (SNC) of the Scandinavian Caledonides records a well-documented history of high pressure (HP) and ultra-high pressure (UHP) metamorphism. Eclogites of the SNC occur in two areas in Sweden, namely Jamtland and Norrbotten. The Jamtland eclogites and associated rocks are well-studied and provide evidence for late Ordovician UHP metamorphism, whereas the Norrbotten eclogites, formed during the late Cambrian (Furongian)/Early Ordovician, have not been studied in such detail, especially in terms of the P-T conditions of their formation. Within the studied eclogite, clinopyroxene contains a high-Na core and two rims: inner, medium-Na and outer, low-Na. Garnet consists of a high-Ca euhedral core, low-Ca inner rim and medium-Ca outer rim. A similar pattern occurs within phengite, where high-Si cores are enveloped by medium and low-Si rims. The compositions of the mineral cores, inner rims and outer rims reflect three stages in the metamorphic evolution of the eclogite. Applied Quartz-in-Garnet geobarometry, coupled with Zr-in-rutile geothermometry reveal that garnet nucleation (E0 stage) took place at 1.5-1.6GPa and 620-660 degrees C. The eclogite peak-pressure assemblage developed during the E1 stage, it consists of garnet+omphacite+phengite+rutile+coesite? and yields P-T conditions of 2.8-3.1GPa and 660-780 degrees C as constrained by conventional geothermobarometry and thermodynamic modelling in the NCKFMMnASHT system. Later, lower-pressure stages E2 and E3 record conditions of 2.2-2.8GPa, 680-780 degrees C and 2.1GPa, 735 degrees C, respectively. The prograde metamorphic evolution of the eclogite is inferred from inclusions of epidote, amphibole and clinopyroxene within garnet. The presence of amphibole-quartz-plagioclase symplectites, secondary epidote/zoisite and titanite replacing rutile record the later retrograde changes taking place at <1.5GPa (referred as E4 stage). The obtained P-T conditions indicate that the Norrbotten eclogites underwent a metamorphic evolution characterized by a clockwise P-T path with peak metamorphism reaching up to coesite stability field within a relatively cold subduction regime (7.8 degrees C/km). The obtained results provide the first evidence for UHP metamorphism in the SNC above the Arctic Circle and document cold subduction regime and multistage exhumation of the deeply subducted Baltican margin at early stage of the Caledonian Orogeny.
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| 7. |
- Jaranowski, Maciej, et al.
(författare)
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U-Pb and trace element zircon and apatite petrochronology of eclogites from the Scandinavian Caledonides
- 2023
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Ingår i: Contributions to Mineralogy and Petrology. - : Springer. - 0010-7999 .- 1432-0967. ; 178
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Tidskriftsartikel (refereegranskat)abstract
- The petrochronological records of eclogites in the Scandinavian Caledonides are investigated using EPMA and LA-ICPMS of zircon and apatite for U-Pb geochronology, combined with major and trace element characteristics. Metamorphic zircon from two eclogites from the Lofoten-Vesteralen Complex (Lofoten Archipelago region) collectively yielded a Concordia age 427.8 & PLUSMN; 5.7 Ma and an upper intercept U-Pb age 425 & PLUSMN; 30 Ma. Apatites from the same eclogites provided U-Pb lower intercepts at 322 & PLUSMN; 28 Ma and 354 & PLUSMN; 33 Ma, with the latter also yielding a younger age of 227 & PLUSMN; 24 Ma. Two eclogites from the Lower Seve Nappe (Northern Jamtland) demonstrate different zircon and apatite age records. Metamorphic zircon provided Concordia ages of 467.2 & PLUSMN; 5.9 Ma and 444.5 & PLUSMN; 5.5 Ma, which resolve the age of prograde metamorphism and zircon growth during retrogression, respectively. The lower intercept U-Pb ages of apatites from the same eclogites are 436 & PLUSMN; 18 and 415 & PLUSMN; 25 Ma, respectively. In combination with their geochemical characteristics, they suggest two separate stages of exhumation of eclogite bodies in the Lower Seve Nappe. Zircons from an eclogite from the Blaho Nappe (Nordoyane Archipelago) yielded a continuum of concordant U-Pb dates from ca. 435 to 395 Ma, which suggests several cycles of HT metamorphism within short intervals. Distinctive trace element characteristics of apatites from the Blaho Nappe eclogite suggest formation coeval with zircon and garnet during HT metamorphism, but Pb diffusion behaved as an open system until cooling during exhumation of the nappe at 390 & PLUSMN; 12 Ma (lower intercept U-Pb age of apatite). To summarize, this study presents the high potential of coupled zircon and apatite petrochronology of eclogites in resolving their metamorphic evolution, particularly with respect to using trace element characteristics of apatites to constrain the records of their growth, alterations and the meaning of their U-Pb age record.
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| 8. |
- Kosminska, Karolina, et al.
(författare)
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Blueschist facies metamorphism in Nordenskiold Land of west-central Svalbard
- 2014
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Ingår i: Terra Nova. - : Wiley. - 0954-4879 .- 1365-3121. ; 26:5, s. 377-386
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Tidskriftsartikel (refereegranskat)abstract
- Recent fieldwork in Nordenskiold Land, Svalbard's Southwestern Basement Province, has established the presence of high-pressure (HP) lithologies. They are strongly retrogressed blueschists consisting mainly of garnet and Ca-amphibole with remnants of ferroglaucophane and phengite. The pressure-temperature (P-T) conditions were estimated using phase equilibrium modelling in the NCKFMMnASHTO system. P-T estimates based on the garnet, phengite and ferroglaucophane compositional isopleths and modelled paragenetic assemblage indicate peak metamorphism at 470-490 degrees C and 14-18 kbar. These data fall close to the 7-8 C km(-1) geo-therm, which is similar to that from Motalafjella, the only previously known occurrence of blueschists in Svalbard's Caledonides. The newly discovered blueschists could have formed during the early stage of the Caledonian Orogeny and may represent a vestige of missing marginal basins of the western Iapetus developed at the onset of subduction. The likely counterpart to Svalbard's blueschists is the ophiolitic sequence in the Pearya Terrane of northern Ellesmere Island.
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| 9. |
- Kosminska, Karolina, et al.
(författare)
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Deciphering late Devonian-early CarboniferousP-T-tpath of mylonitized garnet-mica schists from Prins Karls Forland, Svalbard
- 2020
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Ingår i: Journal of Metamorphic Geology. - : WILEY. - 0263-4929 .- 1525-1314. ; 38:5, s. 471-493
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Tidskriftsartikel (refereegranskat)abstract
- Quartz-in-garnet inclusion barometry integrated with trace element thermometry and calculated phase relations is applied to mylonitized schists of the Pinkie unit cropping out on the island of Prins Karls Forland, western part of the Svalbard Archipelago. This approach combines conventional and novel techniques and allows deciphering of the pressure-temperature (P-T) evolution of mylonitic rocks, for which theP-Tconditions could not have been easily deciphered using traditional methods. The results obtained suggest that rocks of the Pinkie unit were metamorphosed under amphibolite facies conditions at 8-10 kbar and 560-630 degrees C and mylonitized at ~500 to 550 degrees C and 9-11 kbar. TheP-Tresults are coupled with in-situ Th-U-total Pb monazite dating, which records amphibolite facies metamorphism atc.359-355 Ma. This is the very first evidence of late Devonian-early Carboniferous metamorphism in Svalbard and it implies that the Ellesmerian Orogeny on Svalbard was associated with metamorphism up to amphibolite facies conditions. Thus, it can be concluded that the Ellesmerian collision between the Franklinian margin of Laurentia and Pearya and Svalbard caused not only commonly accepted brittle deformation and weak greenschist facies metamorphism, but also a burial and deformation of rock complexes at much greater depths at elevated temperatures.
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| 10. |
- Kosminska, Karolina, et al.
(författare)
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Monazite in the eclogite and blueschist of the Svalbard Caledonides : its origin and forming-reactions
- 2023
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Ingår i: Contributions to Mineralogy and Petrology. - : Springer. - 0010-7999 .- 1432-0967. ; 178
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Tidskriftsartikel (refereegranskat)abstract
- High-pressure low-temperature rocks from Svalbard are an excellent target for studying metamorphic reactions in Phanerozoic subduction zones. This study reveals the presence of monazite in an eclogite and a blueschist from the Vestgotabreen Complex, southwestern Svalbard. In order to investigate the monazite-forming reaction, we obtained pressure-temperature estimates coupled with U-Pb and Lu-Hf dating. Combined geothermobarometry allows to constrain three evolutionary stages of garnet growth in the eclogite: nucleation (1.6 & PLUSMN; 0.3 GPa at 460 & PLUSMN; 60 & DEG;C), peak-pressure (2.3 & PLUSMN; 0.3 GPa at 507 & PLUSMN; 60 & DEG;C), and peak-temperature (2.1 & PLUSMN; 0.3 GPa at 553 & PLUSMN; 60 & DEG;C). A zircon age of 482 & PLUSMN; 10 Ma is interpreted to belong to the prograde part of the pressure-temperature path. Monazite forms inclusions within garnet rims, or it is surrounded by allanite and apatite, altogether forming pseudomorphs of a tabular shape in the matrix. Textures, geothermobarometry and geochronology support the conclusion the monazite formed under high-pressure conditions at 471 & PLUSMN; 6 Ma. We propose that the monazite crystallization in the eclogite happened due to a decomposition of accessory phases during the decompression after peak-pressure of the metamorphic cycle. Monazite in the blueschist occurs as inclusions in garnet cores and gives an indicative age of 486 & PLUSMN; 6 Ma, which is interpreted to reflect the prograde growth of the garnet. Lu-Hf garnet dating resolves an age of peak-pressure metamorphism in the blueschist at 471.1 & PLUSMN; 4 Ma under conditions of 2.0 & PLUSMN; 0.03 GPa and 500 & PLUSMN; 30 & DEG;C. The Vestgotabreen Complex provides evidence for an early Ordovician modern-style subduction system in the proximity of the Baltica margin. Hence, this study also supports the tectonic models that favour a mixed Baltican and Laurentian provenance of south-western Svalbard.
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